You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Gallo.jpg|1008" />
  </query-continue>
  <query>
    <pages>
      <page pageid="27" ns="0" title="Faena" />
      <page pageid="48" ns="0" title="El amigo" />
      <page pageid="70" ns="0" title="Los 40 cuartos" />
      <page pageid="536" ns="0" title="Contracampo" />
      <page pageid="629" ns="0" title="Ceramiqueros de Traslasierra" />
      <page pageid="862" ns="0" title="Yira Yira" />
      <page pageid="875" ns="0" title="Las operaciones del Dr. Posadas" />
      <page pageid="926" ns="0" title="Gaudí asesinado por un tranvía" />
      <page pageid="1006" ns="0" title="La Revolución de Mayo" />
      <page pageid="1209" ns="14" title="Categoría:Dolly Pussi" />
    </pages>
  </query>
</api>